if you've got the mods & skins installed for our League, you will join fine to us, but you can't know ahead of joining what other servers are running without some investigation, un fortunately, so this will happen a lot on other servers.
yea... I was a little bit scared whats going on, because I though that if you haven't some skins or mods or you have something which server doesn't then you wont be able to join, but this was weird